The primary objective of this Mentored Patient-Oriented Career Development Award is to develop the skills and experience required to become a successful independent clinical investigator. In order to attain this objective, a training program has been constructed to foster: 1. Advanced training in the methods of epidemiology, biostatistics, and clinical trial design 2. A superior research environment made up of senior clinical investigators and well recognized experts in fields related to the scientific proposal 3. The groundwork on which to build future research projects and collaborations The scientific objective of this proposal is to explore the determinants of altered body composition in rheumatoid arthritis (RA). In RA, lean body mass is 10-15% lower than in non-RA controls despite the preservation of body weight. This observation suggests a net gain in fat mass. This has not been confirmed, however, and no studies have examined regional patterns of fat and muscle distribution in RA. In particular, patterns of fat deposition, particularly fat localized to the abdominal cavity (visceral fat) has emerged as a potent predictor of metabolic syndrome and cardiovascular disease. Further, an increase in fat mass combined with a net loss in lean body mass, termed sarcopenic obesity, has been associated with metabolic syndrome, cardiovascular disease, and mortality in non-RA populations. The specific aims of this proposal are to: 1. Characterize body composition and identify the prevalence of sarcopenic, obesity, and sarcopenic obesity in patients with RA compared to matched non-RA controls 2. Characterize serum adipokine profiles, insulin resistance, and the prevalence of components of the metabolic syndrome in patients with RA compared to matched non-RA controls. 3. Identify the inflammatory and non-inflammatory factors associated with altered body composition phenotypes, adipokine profiles, and insulin resistance in patients with RA .